The present invention relates generally to foundry molds and more particularly to a pattern device useful in the manufacture of the upper part of the foundry mold. The pattern device of the present invention is of the type utilizing an upper trough pattern which is configured to form a trough including a basin in the mold upper part, with at least two gates extending from the trough being formed by gate pins associated with the upper trough pattern.
In a casting method previously known from Swiss Pat. No. 320,832, liquid metal flows from a common mold basin through troughs on the upper side of the upper mold part into vertical gates and through channels located below and adjoining the parting plane into cavities of the mold.
In the terminology related to molds of this type, the basin located on the upper side which includes the troughs and the vertical gates is referred to as the upper trough in contrast to the horizontal lower trough which adjoins the parting plane of the mold and which is downstream of the vertical gates.
It is known to mold the upper trough by means of a separate upper trough pattern which is attachable to a match plate.
In addition to the pattern for the basin, the upper trough pattern also comprises a pattern for the troughs connecting the basin and the gates which is resiliently supported on the pattern device above the patterns for the gates. The resilient mounting of the upper trough pattern is so designed with regard to the gate pins forming the vertical gates that the upper trough pattern projects beyond the upper part of the mold after the mold is finished by compacting.
Pouring of molds having upper troughs of the type previously described has found considerable acceptance particularly with regard to the mass production of castings. This has occurred due to the fact that, if the upper trough cannot be used in a normal manner due to the location of the gates, the use of a special upper trough presents no problems from an economic point of view. Additionally, when filling molds for mass production operations, patterns for the upper troughs can be designed so as to include at least three gate pins which need not be positioned in a straight line. Therefore, the upper trough pattern can be safely placed on the pattern device without additional supporting pins.
However, if the conventionally known methods of filling a mold having an upper trough are applied to the production of castings of a special-order type, certain difficulties will be encountered. In order to maintain the cost of the pattern as low as possible, the pattern device must be made of partial matched plates which can be assembled. These partial matched plates, because of their production cost, should be selected of as small a size as possible, i.e. with the fewest possible patterns per partial pattern plate, inasmuch as experience has shown that the number of castings per customer order can be quite low. On the other hand, the size of partial match plates for the manufacture of special order casting is also influenced by the great diversity of dimensions occurring in individual patterns.
The requirement arising in the production of special order castings which utilize partial match plates of different sizes, wherein the number of molds required differs greatly depending on the respective quantities ordered, necessitates not only quick changeability of individual partial match plates, but also gives rise to demands for a casting system adaptable to the constantly changing demands made thereupon.
Further complications arise when liquid metals are poured whose analyses must be selected as a function of the wall thickness, or where mold cooling periods, i.e. the time between the pouring of a mold and the unpacking of a mold, must be flexible for reasons of casting structure.
Studies based upon the aforementioned conditions have led to recognition that the division of an entire pattern area into individual partial plates cannot be performed in an arbitrary manner. The most advantageous solution seems to involve the possibility of arranging all partial match plates on a main trough on both sides of the match plate plane in a random sequence. Only if the mold dimensions are particularly large does it normally become expedient to fill the mold by means of two separate main troughs, each having partial match plates on both sides arranged in an arbitrary sequence.
Accordingly, it will be seen that the filling of such molds by using upper troughs entails restrictions in that all gates must be arranged in most cases in a straight line because they must empty into the main trough. In practice, known pattern devices utilized in molding of upper troughs are provided in such cases with additional supporting pins so that they can be safely placed on the pattern device. If the aforementioned type of plate geometry is employed, these supporting pins must support themselves upon the actual pattern surface. As a result, the available pattern area cannot be fully utilized due to the location of the supporting pins which must be taken into consideration. Furthermore, the arrangement of the partial match plates in any desired sequence is also not possible for similar reasons. It is a particularly disturbing fact that the cavities automatically originating in the manufacture of the mold due to the supporting pins must be closed by the insertion of special cores into the upper trough before the mold is filled. Due to the fact that techniques involving pouring of molds having an upper trough are becoming in more widespread use, particularly for molds which are produced on turntable molding machines wherein the mold devices are subjected to severe horizontal acceleration during turning operations, the stability of the upper trough patterns must meet stricter and stricter requirements.
The present invention is intended to eliminate many of the above-mentioned disadvantages arising in the utilization of pattern devices having upper trough patterns. The device of the present invention is so structured that the gate pins may be configured to act as retaining pins thereby stabilizing the location of the pattern device and of the upper trough pattern. A particularly advantageous characteristic of the present invention arises by virtue of the fact that where more than two gate pins are involved, two of the gate pins positioned at opposite ends of an upper trough pattern may operate not only as retaining pins, but also as anti-rotation pins preventing rotation of the pattern device about either of the pins. By utilization of the present invention, a plurality of other gate pins may be positioned intermediate the two outermost pins without requiring additional structure to stabilize the pattern device.